1. Field of the Invention
The present invention relates to solar energy and the collection of rays of solar energy and more particularly relates to an improved solar-radiation collection apparatus. More particularly, the present invention relates to a means for tracking the sun and indicating its position relative to the collector and thereafter identifying the position by means of an electrical switch which is activated by the solar rays themselves.
There is a need for devices to collect solar radiation and more particularly to assure that devices which collect solar radiation are properly oriented so as to maximize collection of the solar radiation by facing the sun directly. Generally, solar collectors have required structural rigidity and precise individual alignments of the various elements of a solar collecting array. Thus, it can be appreciated that if solar energy falls in a perpendicular fashion upon the surface of a solar cell, the energy conversion is at a maximum. The attitude and elevation of a flat solar panel can provide a known maximum conversion of solar energy over a given solar day throughout the year and thus generate a maximum watt hour per day. However, the number of solar cells required on a fixed flat panel for a usable power station, considering the various positions of the sun throughout the year is extremely large so that often a system for a given potential commercial or industrial or residential user is prohibitively expensive. Further, the size of such a system can be unusable requiring heavy structural frames and supports to provide adequate load carrying capabilities in view of the weight of such units as well as wind and snow load.
Thus, the use of a tracking mechanism to insure that the cells are directly perpendicular to the incoming sunlight solves many of the problems of static systems having poor incidents with the sunlight in a majority of time situations.
Many devices have been patented which have attempted to solve the problem of a solar radiation system which provides a sun tracking capability.
See, for example, U.S. Pat. No. 4,086,485 entitled "Solar Radiation Collection Apparatus with Tracking Circuitry".
A plurality of collectively controlled mirrors are used for concentrating solar radiation in U.S. Pat. No. 4,102,326 entitled "Central Receiver Solar Collector Using Mechanically Linked Mirrors".
U.S. Pat. No. 4,137,897 provides a "Unified Array for Collection and Concentration of Solar Energy". In that patent there is provided a support included a terraced support structure. A plurality of reflective collector elements are mounted on the terraced support in closely spaced apart relationship. Each of the collector elements are driven in a tracking relationship with the sunlight continuously reflecting energy toward an energy receiver.
A "Sun-Tracking Control System for Solar Collector" is the subject of U.S. Pat. No. 4,146,785.
In U.S. Pat. No. 4,146,784 a "Sun Tracking Device" is provided having an opaque housing with a photosensor located within the opaque housing. A reflector member is disposed within the housing and has an at least partly positively curved shaped position relative to the photosensor such that the rays of the sun striking it will be reflected onto the photosensor. An opening in the opaque housing together with the reflector member defines a minimum defined angle and a circuit connected to the photosensor is provided for utilizing output of the photosensor.
A "Radiation Tracking Control" is the subject of U.S. Pat. No. 4,179,612. In that patent photosensors receive incident radiation from the sun.
An edge means intercepts radiation directed toward each sensor so that a primary and secondary location on each sensor respectively receive and do not receive incident radiation and the sensors control the tracking movement of the apparatus. The sensors are electrically energized and have electrical outputs which vary a function of radiation interception by the sensors and there is provided means responsive to the outputs to control the tracking movement. A control means connected with the sensors and responsive to increases and decreases in the intensity of the radiation responsively decreases and increases electrical energization of the sensors.
A "Heliostat Guidance" apparatus is the subject of U.S. Pat. No. 4,211,922. In that patent, there is an apparatus for positioning a mirror to receive solar radiation from the sun onto a remote receiver and provides an apparatus for properly aiming the heliostat.
U.S. Pat. No. 4,223,174 provides a "Sun-Tracking Solar Energy Conversion System". In that patent, a number of solar energy converter assemblies are carried by a support frame which is mounted for independent rotation about a horizontal and vertical axis. Sensors detect the position of the sun; and control circuitry positions the support frame in elevation and azimuth so that converter assemblies track and face the sun whenever the sun incident energy is greater than a threshold level of about 25 percent of normal. Each converter assembly includes a solar cell and a multiangular conical concentrator shell for collecting, concentrating and directing incident solar energy onto the solar cell.
A solar tracking device which tracks the position of the sun using paired, partially shaded photocells is the subject of U.S. Pat. No. 4,225,781 entitled "Solar Tracking Apparatus". Auxiliary photocells are used for initial acquisition of the sun and for the suppression of false tracking when the sun is obscured by clouds.
U.S. Pat. No. 4,267,441 provides an "Energy Rays Tracking Device". In that patent, there is provided a receiver for fixing a position relative to the direction of maximum energy rays, a prime mover for maintaining the alignment of the receiver and an energy rays user, an energy rays tracker for controlling the power to the prime mover in response to the receiver, a timed tracker for controlling the prime mover when the energy rays tracker is not functioning due to energy rays being too diffused, an energy sensitive element for detecting the presence or absence of energy rays, and a power controller responsive to the energy sensitive element for repositioning the receiver and the energy rays user for the following period of tracking.
U.S. Pat. No. 4,269,168 provides a "Focusing Reflector Solar Energy Collector Apparatus and Method".
Many of these prior art devices are highly complex and would be expensive to construct and maintain. Many have dynamic-type tracking systems which require continual movement of the assembly in order to continue tracking of the sun.
Thus there is a need for a highly simplified solar tracking mechanism which will accurately and reasonably position the sun depending upon its position in the sky.
The present invention solves these prior art problems and shortcomings by providing a solar tracking mechanism which is by and large static and which provides a semispherical hollow collector trough body positioned with the flat uppermost surface of the semisphere substantially horizontal. The uppermost surface thus defines a circle having a center which likewise is a focal point for the innermost hollow portion of the collector trough which is concave and which provides a concave surface having the same focal point as the center of the circle.
A plurality of solar collection modules are mounted within the trough body in a matrix fashion. Each of the modules provides a radial passageway formed in the concave surface along a line intersecting the focal point. A strip of thermally expandable material, a photocell or the like, is mounted within the passageway. A normally open switch is positioned adjacent the thermally expandable strip or connected electrically to the photocell for switching an electrical circuit between on and off positions respectively responsive to expansion or contraction in the case of the thermally expandable strip. Thus, only proper alignment of the sun with a particular passageway will cause solar radiation to fall on the thermally expandable strip and actuate the strip. A shroud in the form of preferably a conically shaped thin wall structure can be provided having perferations therethrough for enhancing the directional definition of the sun's rays.
The above solar tracking mechanism could be used in combination with a computer with the switches being interfaced with the computer by the nature of their position in the array which lines the concave surface so as to give position information to the computer which could then be used to move an array of solar collectors into a desired position of incidents with the sunlight to maximize energy collection at a given time.
It is thus an object of the present invention to provide a solar tracking mechanism which is statis and highly simplified in operation and instruction.
Another object of the present invention is to provide a solar tracking mechanism which is compatible with a variety of solar collection devices.
Another object of the present invention is to provide a solar tracking mechanism which generates position information for use with a computer.
Another object of the present invention is to provide a solar tracking mechanism which generates electrical signals responsive to the position of the sun.